8BChernobyl

Q.3 Describe the impact the disaster has on the environment and people.

The impact of the Chernobyl disaster was felt all over Europe but particularly in the nearby areas of the accident which include Russia, Belarus and what is now known as Ukraine. The disaster has had a lasting affect on both plants and animals but also humans. There has been a large increase in the number or children aged under 14 developing thyroid cancers in the areas which were most affected and many children were born premature, mentally ill or with birth defects. Any land within 150 000 km2 of the disaster site was contaminated with radioactive waste including a forest in which all the trees turned orange and died. Plants were found mutated with oddly shaped leaves and fruit and animals were born with defects. These radioactive particles found in the environment could potentially remain hazardous for thousands of years.
Following the failure of reactor four at the Chernobyl power plant, 50 tons of radioactive particles were released into the atmosphere and as they reacted with the air a fire broke out and produced a large cloud of smoke made of radioactive waste. This cloud drifted right across Europe toward France and the UK and many people were afraid of contamination from food or water affected by the rain from the cloud. There was a shortage in food supplies resulting from the contaminated rain which poisoned water and soil and therefore plants and livestock. The scale of impact on the countries throughout Europe depended on the weather and the amount of rain they received so some areas were affected more than others.
After the fire broke out, the town’s local firemen were called but they did not expect the fire to be of the large scale that it was and had to immediately call in reinforcements. The firemen battled the fire all night, unaware of the extreme radiation levels and that the fire was not a normal fire that could be put out by water. Many experienced sickness caused by the levels of radiation which led to tiredness, vomiting, bleeding and the loss of hair and teeth. The following day, none of the people in the town of Chernobyl and the nearby town of Pripyat were told of the dangers of what had happened. When it was revealed that the fire would continue burning for weeks, if not months, it was decided that they would bury it in clay, sand, lead and boron. After 14 days the fire was finally put out but before that people began to be evacuated. Close to 135 000 people were evacuated and taken outside a 30km safety zone by buses sent from the nearest large city, Kiev but they had already been exposed to about 36 hours of radiation. 54 people died immediately, most were fire fighters, rescue workers or workers on the sight and a further 4 000 to 24 000 died not long after due to high levels of radiation.
28 years on the towns still experience low levels of radiation and have not since been repopulated.

Alexander Akimov and his fellow workers were just trying to do their job , testing the reactor, Making an experiment with the reactor which involved disabling its safety features .By doing so it would mean the power output of the reactor would be dropped in preparation for the up coming test.the reactor's power output dropped too much, almost to zero. Because of this drop they tried to bring the power back by removing some of the control roads. The reactor had several other features which were regarded as unsafe in the Soviet Union as well as by experts from other countries .The goal of the experiment was to see if the station's turbine generator could deliver temporary power to certain cooling pumps after it was cutoff of its steam supply. As a first step, the unit's operators deliberately dissconected the reactor's emergency core cooling system; such a system is necessary because every large reactor core can generate millions or billions of watts of thermal power . This energy must constantly be removed by a flow of coolant or the core may cause a steam explosion, melt down, or even a relatively small nuclear explosion. The emergency core cooling system is supposed to keep the core cool when the usual systems have failed. Unit No. 4's operators had not left the emergency core cooling system disconnected, but had committed a lot of mistakes which allowed the reactor's power output to fall far below planned levels. The operators tried to restore the reactor's power output but instead the operators caused it to go out of control. In approximately 5 seconds, the core's heat output increased exponentially to the point where a steam explosion occurred. This blew a 1,000-ton concrete lid off the reactor and damaged the roof of the reactor hall. A few seconds later, an even larger explosion occurred when hydrogen released by the breakdown of water exploded. Burning chunks of graphite (a form of carbon of which 1700 tons were present in the reactor core) flew through the air and landed on other parts of the complex, starting fires. The remaining graphite started to burn, releasing a plume of radioactive smoke that was carried by the wind first north, toward Scandinavia, and later west and south over much of the rest of Europe. The graphite fire burned for over a week, but was finally brought under control by firefighters, many of whom died of radiation burns. The reactor was eventually encased in a shell of concrete. In the late 1990s, United States and Ukrainian engineers worked together to evaluate conditions inside the sarcophagus, which may be vulnerable to collapse in an earthquake. The sarcophagus may need to be strengthened to prevent future releases of radioactivity from the site. More preparation for the test continued later when they decided two pumps will be switched on in the cooling system. By doing so the water flow was increased out of the reactor and this removed heat more quickly. This also caused a low level of water in the steam separator. Because of the low level of water in the steam separator , the amount of feed water increased coming into the operator. More control roads were taken out of the reactor to raise internal reactor temperature and pressure, people hoped that it would cause the water level and steam separator to rise. The water in the steam separator did start to rise , so then the operator adjusted the flow of the feed water by lowering it .This decreased the amount of heat being removed from the reactor core. Because many of the control rods had been removed and the amount of heat being taken from the core by the coolant had been reduced , it began to get very hot. the amount of incoming water had been decreased as well and there was relatively low pressure in the core. The coolant inside the core began to boil to form steam which was caused by the heat and the low pressure. In order to prevent the reactor from shutting itself off from xenon poisoning, the operators pulled the control rods almost all the way out. This caused an enormous increase in the nuclear reaction to many times the reactor's normal power level. This caused a steam explosion that blew the top off the reactor, probably stopping the nuclear reaction. Then the carbon caught fire and burned for about nine days. This scattered the reactor contents and large amounts of radioactivity. At this plant the worst reactor disaster to ever occur took place on April 26, 1986. It happened largely because normal reactor operations were suspended; an experiment was to take place in the reactor. As a result, normal safety guidelines were disregarded, and the accident occurred. However, as with most accidents of this type, it was a result of many small mistakes adding up to create a catastrophe.

As a result of the Chernobyl disaster in 1986, many things were learnt regarding the safety of nuclear reactors. There has been more concern for the safety standards of nuclear reactors and changes have been made to them.
Following the Chernobyl incident, the reactor in which the fire broke out was sealed in a large concrete shelter to stop the emission of radioactive particles. In the 1900s, 400 million US dollars were invested into improving the safety of the plant and its remaining reactors but not long after, in 2000 the final reactor was shut down at the Chernobyl Nuclear Power Plant.
Other reactors similar to the Chernobyl plant made changes to improve their safety including modifications to the cooling system and control rods which makes it safer for the plant to run at low power. Their automatic shut-down systems have also been enhanced to prevent a repeat of the Chernobyl disaster from ever occurring.
Scientists are now aware of the effect radioactive pollution can have on both people and the environment and are equipped to deal with a disaster like this quickly and safely.